Dihydropyranopyrimidines for the treatment of viral infections

ABSTRACT

This invention relates to dihydropyranopynmidine derivatives, processes for their preparation, pharmaceutical compositions, and their use in treating viral infections.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase entry of International Application No. PCT/EP2017/066307, filed on Jun. 30, 2017, which claims priority to EP Patent Application No. 16177401.3, filed Jul. 1, 2016, each of which is incorporated herein in its entirety.

This invention relates to dihydropyranopyrimidine derivatives, processes for their preparation, pharmaceutical compositions, and their use in treating viral infections.

The present invention relates to the use of dihydropyranopyrimidine derivatives in the treatment of viral infections, immune or inflammatory disorders, whereby the modulation, or agonism, of toll-like-receptors (TLRs) is involved. Toll-Like Receptors are primary transmembrane proteins characterized by an extracellular leucine rich domain and a cytoplasmic extension that contains a conserved region. The innate immune system can recognize pathogen-associated molecular patterns via these TLRs expressed on the cell surface of certain types of immune cells. Recognition of foreign pathogens activates the production of cytokines and upregulation of co-stimulatory molecules on phagocytes. This leads to the modulation of T cell behaviour.

It has been estimated that most mammalian species have between ten and fifteen types of Toll-like receptors. Thirteen TLRs (named TLR1 to TLR13) have been identified in humans and mice together, and equivalent forms of many of these have been found in other mammalian species. However, equivalents of certain TLR found in humans are not present in all mammals. For example, a gene coding for a protein analogous to TLR10 in humans is present in mice, but appears to have been damaged at some point in the past by a retrovirus. On the other hand, mice express TLRs 11, 12, and 13, none of which are represented in humans. Other mammals may express TLRs which are not found in humans. Other non-mammalian species may have TLRs distinct from mammals, as demonstrated by TLR14, which is found in the Takifugu pufferfish. This may complicate the process of using experimental animals as models of human innate immunity.

For reviews on TLRs see the following journal articles. Hoffmann, J. A., Nature, 426, p 33-38, 2003; Akira, S., Takeda, K., and Kaisho, T., Annual Rev. Immunology, 21, p 335-376, 2003; Ulevitch, R. J., Nature Reviews: Immunology, 4, p 512-520, 2004.

Compounds indicating activity on Toll-Like receptors have been previously described such as purine derivatives in WO 2006/117670, quinazoline derivatives in WO 2012/156498 and substituted benzoazepines in WO 2007/024612, and pyrimidines in WO 2012/136834.

However, there exists a strong need for novel Toll-Like receptor modulators having preferred selectivity, higher potency, and an improved safety profile compared to the compounds of the prior art.

In accordance with the present invention a compound of formula (I, II, or III) is provided

or a pharmaceutically acceptable salt, tautomer(s), stereo-isomeric form, solvate or polymorph thereof, wherein R₁ is C₁₋₆ alkyl optionally substituted by one or more substituents independently selected from alcohol or C₁₋₃ alkoxy; R₂ is selected from hydrogen, fluorine, C₁₋₃ alkyl, cyclopropyl, —CF₃, C₁₋₃ alkoxy or nitrile.

Preferred compounds of formulas I and II include the structures below:

The most preferred compound, of formula III, has the following structure:

The compounds of formula (I, II, III) and their pharmaceutically acceptable salts, tautomer(s), stereo-isomeric forms, solvate or polymorph thereof have activity as pharmaceuticals, in particular as modulators of Toll-Like Receptors 7 and 8 (especially TLR 8).

In a further aspect the present invention provides a pharmaceutical composition comprising a compound of formula (I, II, III) or a pharmaceutically acceptable salt, tautomer, stereo-isomeric form, solvate or polymorph thereof together with one or more pharmaceutically acceptable excipients, diluents or carriers.

Furthermore, a compound of formula (I, II, III) or a pharmaceutically acceptable salt, solvate, tautomer, stereo-isomeric form or polymorph thereof according to the current invention, or a pharmaceutical composition comprising said compound of formula (I, II, III) or a pharmaceutically acceptable salt, solvate, tautomer, stereo-isomeric form or polymorph thereof can be used as a medicament.

Another aspect of the invention is that a compound of formula (I, II, III) or its pharmaceutically acceptable salt, solvate, tautomer, stereo-isomeric form or polymorph thereof, or said pharmaceutical composition comprising said compound of formula (I, II, III) or a pharmaceutically acceptable salt, solvate, tautomer, stereo-isomeric form or polymorph thereof can be used accordingly in the treatment of a disorder in which the modulation of TLR7 and/or TLR8 is involved preferably TLR8.

The term “(C₁₋₃)-alkyl” or “(C₁₋₆)-alkyl” refers to a straight-chain, branched-chain or cyclic saturated aliphatic hydrocarbon containing the specified number of carbon atoms.

The term “cycloalkyl” refers to a carbocyclic ring containing the specified number of carbon atoms such as cyclo-propyl.

The term “alkoxy” refers to an alkyl (carbon and hydrogen chain) group singular bonded to oxygen (e.g. methoxy group or ethoxy group) such as C₁₋₃ alkoxy.

As used herein, any chemical formula with bonds shown only as solid lines and not as solid wedged or hashed wedged bonds, or otherwise indicated as having a particular configuration (e.g. R, S) around one or more atoms, contemplates each possible stereoisomer, or mixture of two or more stereoisomers.

The terms “stereoisomers”, “stereoisomeric forms” or “stereochemically isomeric forms” hereinbefore or hereinafter are used interchangeably.

The invention includes all stereoisomers of the compounds of the invention either as a pure stereoisomer or as a mixture of two or more stereoisomers.

Enantiomers are stereoisomers that are non-superimposable mirror images of each other. A 1:1 mixture of a pair of enantiomers is a racemate or racemic mixture.

Diastereomers (or diastereoisomers) are stereoisomers that are not enantiomers, i.e. they are not related as mirror images. If a compound contains a double bond, the substituents may be in the E or the Z configuration. If a compound contains an at least disubstituted non-aromatic cyclic group, the substituents may be in the cis or trans configuration.

Therefore, the invention includes enantiomers, diastereomers, racemates, E isomers, Z isomers, cis isomers, trans isomers and mixtures thereof, whenever chemically possible.

The meaning of all those terms, i.e. enantiomers, diastereomers, racemates, E isomers, Z isomers, cis isomers, trans isomers and mixtures thereof are known to the skilled person.

The absolute configuration is specified according to the Cahn-Ingold-Prelog system. The configuration at an asymmetric atom is specified by either R or S. Resolved stereoisomers whose absolute configuration is not known can be designated by (+) or (−) depending on the direction in which they rotate plane polarized light. For instance, resolved enantiomers whose absolute configuration is not known can be designated by (+) or (−) depending on the direction in which they rotate plane polarized light.

When a specific stereoisomer is identified, this means that said stereoisomer is substantially free, i.e. associated with less than 50%, preferably less than 20%, more preferably less than 10%, even more preferably less than 5%, in particular less than 2% and most preferably less than 1%, of the other stereoisomers. Thus, when a compound of Formula (I) is for instance specified as (R), this means that the compound is substantially free of the (S) isomer; when a compound of Formula (I) is for instance specified as E, this means that the compound is substantially free of the Z isomer; when a compound of Formula (I) is for instance specified as cis, this means that the compound is substantially free of the trans isomer.

Pharmaceutically acceptable salts of the compounds of formula (I), (II) or (III) include the acid addition and base salts thereof. Suitable acid addition salts are formed from acids which form non-toxic salts. Suitable base salts are formed from bases which form non-toxic salts.

The compounds of the invention may also exist in unsolvated and solvated forms. The term “solvate” is used herein to describe a molecular complex comprising the compound of the invention and one or more pharmaceutically acceptable solvent molecules, for example, ethanol.

The term “polymorph” refers to the ability of the compound of the invention to exist in more than one form or crystal structure.

The compounds of the present invention may be administered as crystalline or amorphous products. They may be obtained for example as solid plugs, powders, or films by methods such as precipitation, crystallization, freeze drying, spray drying, or evaporative drying. They may be administered alone or in combination with one or more other compounds of the invention or in combination with one or more other drugs. Generally, they will be administered as a formulation in association with one or more pharmaceutically acceptable excipients. The term “excipient” is used herein to describe any ingredient other than the compound(s) of the invention. The choice of excipient depends largely on factors such as the particular mode of administration, the effect of the excipient on solubility and stability, and the nature of the dosage form.

The compounds of the present invention or any subgroup thereof may be formulated into various pharmaceutical forms for administration purposes. As appropriate compositions there may be cited all compositions usually employed for systemically administering drugs. To prepare the pharmaceutical compositions of this invention, an effective amount of the particular compound, optionally in addition salt form, as the active ingredient is combined in intimate admixture with a pharmaceutically acceptable carrier, which carrier may take a wide variety of forms depending on the form of preparation desired for administration. These pharmaceutical compositions are desirably in unitary dosage form suitable, for example, for oral, rectal, or percutaneous administration. For example, in preparing the compositions in oral dosage form, any of the usual pharmaceutical media may be employed such as, for example, water, glycols, oils, alcohols and the like in the case of oral liquid preparations such as suspensions, syrups, elixirs, emulsions, and solutions; or solid carriers such as starches, sugars, kaolin, diluents, lubricants, binders, disintegrating agents and the like in the case of powders, pills, capsules, and tablets. Because of their ease in administration, tablets and capsules represent the most advantageous oral dosage unit forms, in which case solid pharmaceutical carriers are obviously employed. Also included are solid form preparations that can be converted, shortly before use, to liquid forms. In the compositions suitable for percutaneous administration, the carrier optionally comprises a penetration enhancing agent and/or a suitable wetting agent, optionally combined with suitable additives of any nature in minor proportions, which additives do not introduce a significant deleterious effect on the skin. Said additives may facilitate the administration to the skin and/or may be helpful for preparing the desired compositions. These compositions may be administered in various ways, e.g., as a transdermal patch, as a spot-on, as an ointment. The compounds of the present invention may also be administered via inhalation or insufflation by means of methods and formulations employed in the art for administration via this way. Thus, in general the compounds of the present invention may be administered to the lungs in the form of a solution, a suspension or a dry powder.

It is especially advantageous to formulate the aforementioned pharmaceutical compositions in unit dosage form for ease of administration and uniformity of dosage. Unit dosage form as used herein refers to physically discrete units suitable as unitary dosages, each unit containing a predetermined quantity of active ingredient calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. Examples of such unit dosage forms are tablets (including scored or coated tablets), capsules, pills, powder packets, wafers, suppositories, injectable solutions or suspensions and the like, and segregated multiples thereof.

Those of skill in the treatment of infectious diseases will be able to determine the effective amount from the test results presented hereinafter. In general it is contemplated that an effective daily amount would be from 0.01 mg/kg to 50 mg/kg body weight, more preferably from 0.1 mg/kg to 10 mg/kg body weight. It may be appropriate to administer the required dose as two, three, four or more sub-doses at appropriate intervals throughout the day. Said sub-doses may be formulated as unit dosage forms, for example, containing 1 to 1000 mg, and in particular 5 to 200 mg of active ingredient per unit dosage form.

The exact dosage and frequency of administration depends on the particular compound of formula (I), (II) or (III) used, the particular condition being treated, the severity of the condition being treated, the age, weight and general physical condition of the particular patient as well as other medication the individual may be taking, as is well known to those skilled in the art. Furthermore, it is evident that the effective amount may be lowered or increased depending on the response of the treated subject and/or depending on the evaluation of the physician prescribing the compounds of the instant invention. The effective amount ranges mentioned above are therefore only guidelines and are not intended to limit the scope or use of the invention to any extent.

PREPARATION OF COMPOUNDS OF FORMULA (I)

2-amino-7,8-dihydro-5H-pyrano[4,3-d]pyrimidin-4-ol (1). To a suspension of guanidine hydrochloride (906 mg, 9.48 mmol) in ethanol (30 mL) was added sodium ethoxide (4.03 mL, 9.48 mmol) and the resulting mixture was stirred at room temperature for 10 min before addition of methyl 4-oxotetrahydro-2H-pyran-3-carboxylate (1.00 g, 6.32 mmol) in ethanol (35 mL). The reaction mixture was heated at 80° C. overnight then concentrated to dryness, the residue was diluted with water and the pH was adjusted to 4 with HCl (1N, aq.). The resulting mixture was stirred at room temperature for 2 hours. The precipitated solids were isolated by filtration, washed with water and dried in vacuo to give the titled compound as a light yellow solid (860 mg, 81%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.36 (t, J=5.56 Hz, 2H), 3.77 (t, J=5.56 Hz, 2H), 4.24 (s, 2H), 6.34 (s, 2H), 10.78 (s, 1H).

4-chloro-7,8-dihydro-5H-pyrano[4,3-d]pyrimidin-2-amine (2). A mixture of 2-amino-7,8-dihydro-5H-pyrano[4,3-d]pyrimidin-4-ol (450 mg, 2.69 mmol) in POCl₃ (6 mL) was heated to 100° C. for 5 hours then at room temperature overnight. The reaction mixture was concentrated and K₂CO₃ (sat., aq.) was added slowly (until pH=8). The resulting aqueous suspension was extracted thrice with EtOAc. The combined organic layers were washed with brine, dried over Na₂SO₄, the solids were removed by filtration and concentrated to give the titled compound as a pale yellow solid (370 mg, 74%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.64 (t, J=5.81 Hz, 2H), 3.89 (t, J=5.81 Hz, 2H), 4.47 (s, 2H), 6.89 (s, 2H). LC-MS RT: 1.64 min, m/z=186.3, Method A)

N⁴-butyl-7,8-dihydro-5H-pyrano[4,3-d]pyrimidine-2,4-diamine (3). In a sealed tube, to a suspension of 4-chloro-7,8-dihydro-5H-pyrano[4,3-d]pyrimidin-2-amine (220 mg, 1.19 mmol) in 1,4-dioxane (1 mL) was added n-butylamine (0.469 mL, 4.74 mmol). The resulting suspension was heated to 120° C. overnight. The reaction mixture was concentrated and the crude was purified by silica gel column chromatography using a CH₂Cl₂/(CH₃OH, containing 5% aq. NH₃) gradient to afford an oil that was triturated in Et₂O. The resulting solid was isolated by filtration, dried under vacuum to give the titled compound as a pale yellow solid (161 mg, 61%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 0.89 (t, J=7.33 Hz, 3H), 1.29 (m, 2H), 1.48 (m, 2H), 2.40 (t, J=5.56 Hz, 2H), 3.27 (m, 2H), 3.79 (t, J=5.56 Hz, 2H), 4.29 (s, 2H), 5.67 (s, 2H), 6.05 (t, J=5.31 Hz, 1H). LC-MS RT: 1.89 min, m/z=222.9, Method A)

(2R)-2-[(2-amino-7,8-dihydro-5H-pyrano[4,3-d]pyrimidin-4-yl)amino]hexan-1-ol (4, a compound according to Formula I). In a sealed tube, to a suspension of 4-chloro-7,8-dihydro-5H-pyrano[4,3-d]pyrimidin-2-amine (134 mg, 0.722 mmol) in 1,4-dioxane (0.670 mL) was added D-norleucinol (338 mg, 2.89 mmol). The resulting suspension was heated to 120° C. overnight. The reaction mixture was concentrated and the crude product was purified by silica gel column chromatography using a CH₂Cl₂/(CH₃OH, containing 5% aq. NH₃) gradient to give an oil which was triturated in Et₂O. The resulting solid was isolated by filtration, dried under vacuum to give the titled compound as an off-white solid (143 mg, 74%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 0.85 (t, J=6.82 Hz, 3H), 1.20-1.31 (m, 4H), 1.42 (m, 1H), 1.59 (m, 1H), 2.40 (t, J=5.56 Hz, 2H), 3.38 (m, 2H), 3.80 (t, J=5.56 Hz, 2H), 4.13 (m, 1H), 4.28 (d, J=14.15 Hz, 1H), 4.33 (d, J=14.15 Hz, 1H), 4.57 (t, J=5.30 Hz, 1H), 5.54 (d, J=8.08 Hz, 1H), 5.66 (s, 2H). LC-MS RT: 1.86 min, m/z=266.9, Method A). [α]_(D) ²⁰+20.4 (c 0.27, DMF)

PREPARATION OF COMPOUNDS OF FORMULA (II)

2-amino-5,8-dihydro-6H-pyrano[3,4-d]pyrimidin-4-ol (5). To a suspension of guanidine hydrochloride (832 mg, 8.71 mmol) in ethanol (30 mL) was added sodium ethoxide (3.71 mL, 8.71 mmol) and the resulting mixture was stirred at room temperature for 10 minutes before addition of ethyl 3-oxotetrahydro-2H-pyran-4-carboxylate (1.00 g, 5.81 mmol) in ethanol (30 mL). The reaction mixture was heated at 80° C. overnight then was concentrated to dryness, the residue was diluted with water and the pH was adjusted to 4 with (HCl, 1N, aq.). The resulting mixture was stirred at room temperature for 2 hours. The precipitated solid was isolated by filtration, washed with water and dried in vacuo to give the titled compound as a light pink solid (970 mg, 100%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.26 (t, J=5.56 Hz, 2H), 3.75 (t, J=5.56 Hz, 2H), 4.14 (s, 2H), 6.29 (s, 2H), 10.71 (s, 1H).

4-chloro-5,8-dihydro-6H-pyrano[3,4-d]pyrimidin-2-amine(6). A mixture of 2-amino-5,8-dihydro-6H-pyrano[3,4-d]pyrimidin-4-ol (398 mg, 2.38 mmol) in POCl₃ (5.3 mL) was heated to 100° C. for 5 hours then at room temperature overnight. The reaction mixture was concentrated and K₂CO₃ (sat., aq.) was slowly added (until pH=8). The resulting aqueous suspension was extracted thrice with EtOAc. The combined organic layers were washed with brine, dried over Na₂SO₄, the solids were removed by filtration and the solvent of the filtrate was removed under reduced pressure to afford the titled compound as a pale pink solid (231 mg, 52%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 2.55 (t, J=5.81 Hz, 2H), 3.87 (t, J=5.81 Hz, 2H), 4.40 (s, 2H), 6.88 (s, 2H). LC-MS RT: 1.71 min, m/z=186.3, Method A).

N⁴-butyl-5,8-dihydro-6H-pyrano[3,4-d]pyrimidine-2,4-diamine (7). In a sealed tube, to a suspension of 4-chloro-5,8-dihydro-6H-pyrano[3,4-d]pyrimidin-2-amine (150 mg, 0.808 mmol) in 1,4-dioxane (0.7 mL) was added n-butylamine (319 μL, 3.23 mmol). The resulting suspension was heated at 120° C. overnight. The reaction mixture was concentrated under reduced pressure. The crude was purified by silica gel column chromatography using a CH₂Cl₂/(CH₃OH containing 5% aq. NH₃) gradient to give an oil which was triturated in Et₂O. The resulting solid was isolated by filtration, dried under vacuum to give the titled compound as pale yellow solid (128 mg, 71%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 0.89 (t, J=7.33 Hz, 3H), 1.30 (m, 2H), 1.50 (m, 2H), 2.25 (t, J=5.06 Hz, 2H), 3.15-3.19 (m, 1H), 3.26 (m, 2H), 3.82 (t, J=5.56 Hz, 2H), 4.18 (s, 2H), 5.65 (s, 2H), 6.27 (m, 1H). LC-MS RT: 2.01 min, m/z=222.9, Method A)

(2R)-2-[(2-amino-5,8-dihydro-6H-pyrano[3,4-d]pyrimidin-4-yl)amino]hexan-1-ol (8, a compound according to Formula II). In a sealed tube, to a suspension of 4-chloro-5,8-dihydro-6H-pyrano[3,4-d]pyrimidin-2-amine (163 mg, 878 μmol) in 1,4-dioxane (815 μL) was added D-norleucinol (412 mg, 3.51 mmol). The resulting mixture was heated at 120° C. overnight. The reaction mixture was concentrated under reduced pressure. The crude was purified by silica gel column chromatography using a CH₂Cl₂/(CH₃OH containing aq. NH₃ 5%) gradient to give an oil which was triturated in Et₂O. The resulting solid was isolated by filtration, dried under vacuum to give the titled compound as a beige solid (85 mg, 36%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 0.85 (t, J=6.57 Hz, 3H), 1.19-1.33 (m, 4H), 1.44 (m, 1H), 1.60 (m, 1H), 2.27 (m, 2H), 3.35 (m, 1H), 3.42 (m, 1H), 3.83 (t, J=5.56 Hz, 2H), 4.13 (m, 1H), 4.19 (s, 2H), 4.59 (t, J=5.56 Hz, 1H), 5.64 (s, 2H), 5.73 (d, J=8.59 Hz, 1H). LC-MS RT: 1.95 min, m/z=266.9, Method A). [α]_(D) ²⁰+21.8 (c 0.28, DMF)

PREPARATION OF COMPOUNDS OF FORMULA (III)

ethyl 2-diazo-6-hydroxy-3-oxohexanoate (9). To a solution of ethyl diazoacetate (13.4 g, 118 mmol) and dihydrofuran-2(3H)-one (6.75 g, 78.4 mmol) in anhydrous THF (420 mL) under a N₂ atmosphere, was added dropwise a solution of LiHMDS in anhydrous THF (78.4 mL, 118 mmol, 1.5 M) at −78° C. and the reaction mixture stirred at −78° C. for 90 minutes. The reaction mixture was diluted with a NaHCO₃ aqueous solution and the resulting biphasic solution was extracted thrice with EtOAc. The combined organic layers were washed with NH₄Cl (aq.), then brine, dried over MgSO₄, the solids were removed by filtration and the solvent of the filtrate was removed under reduced pressure. The crude was purified by silica gel column chromatography using a heptane/EtOAc gradient to give the titled compound as a yellow oil (5.78 g, 37%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 1.25 (t, J=7.08 Hz, 3H), 1.67 (m, 2H), 2.81 (t, J=7.33 Hz, 2H), 3.40 (td, J=6.50 Hz, J=5.20 Hz, 2H), 4.23 (q, J=7.08 Hz, 2H), 4.45 (t, J=5.20 Hz, 1H).

ethyl 5-hydroxy-3,4-dihydro-2H-pyran-6-carboxylate(10). To a solution of ethyl 2-diazo-6-hydroxy-3-oxohexanoate (5.78 g, 28.9 mmol) in dry toluene (200 mL) was added rhodium (II) acetate dimer (255 mg, 0.577 mmol) and the resulting green suspension was stirred overnight at room temperature and filtered to give a brown solution which was purified by silica gel column chromatography using CH₂Cl₂ as an eluent to give the titled compound as a colorless oil (2.47 g, 45%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 1.24 (t, J=7.07 Hz, 3H), 1.84 (m, 2H), 2.32 (t, J=6.57 Hz, 1H), 3.82 (m, 2H), 4.21 (d, J=7.07 Hz, 2H), 10.19 (s, 1H).

2-amino-7,8-dihydro-6H-pyrano[3,2-d]pyrimidin-4-ol(11). To a suspension of guanidine hydrochloride (1.38 g, 14.4 mmol) in ethanol (45 mL) was added sodium ethoxide (6.14 mL, 14.4 mmol) and the resulting mixture was stirred at room temperature for 10 minutes before addition of a solution of ethyl 5-hydroxy-3,4-dihydro-2H-pyran-6-carboxylate (1.84 g, 9.62 mmol) in ethanol (45 mL). The reaction mixture was heated at 80° C. overnight. The reaction mixture was concentrated to dryness, the residue was diluted with water and the pH was adjusted to 4 with aq. 1N HCl. The resulting mixture was stirred at room temperature overnight. The precipitated solids were filtered, washed with an abundant amount of water and dried in vacuo to give the titled compound as an orange solid (580 mg, 36%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 1.85 (m, 2H), 2.36 (t, J=6.60 Hz, 2H), 3.90 (t, J=5.06 Hz, 2H), 5.90 (s, 2H), 10.76 (s, 1H).

4-chloro-7,8-dihydro-6H-pyrano[3,2-d]pyrimidin-2-amine(12). A mixture of 2-amino-7,8-dihydro-6H-pyrano[3,2-d]pyrimidin-4-ol (580 mg, 3.47 mmol) in phosphorus oxychloride (8 mL) was heated at 115° C. for 30 minutes and cooled down to room temperature. The reaction mixture was concentrated and K₂CO₃ saturated aqueous solution was slowly added (until pH=8). The resulting aqueous suspension was extracted thrice with EtOAc. The combined organic layers were dried over Na₂SO₄, filtered and concentrated to give 343 mg of a pale yellow solid. ¹H NMR (400 MHz, DMSO-d₆) δ ppm 1.97 (m, 2H), 2.66 (t, J=6.60 Hz, 2H), 4.13 (t, J=5.05 Hz, 2H), 6.39 (s, 2H). LC-MS RT: 1.70 min, m/z=186.3, Method A).

N⁴-butyl-7,8-dihydro-6H-pyrano[3,2-d]pyrimidine-2,4-diamine(13). A mixture of 4-chloro-7,8-dihydro-6H-pyrano[3,2-d]pyrimidin-2-amine (150 mg, 0.808 mmol) and n-butylamine (0.319 mL, 3.23 mmol) in 1,4-dioxane (4 mL) was heated at 115° C. overnight. The crude was purified by silica gel column chromatography using a CH₂Cl₂/(CH₃OH containing 5% aq. NH₃) gradient to give an oil which was lyophilized in a mixture of CH₃CN (2 mL) and water (10 mL) to give the titled compound as an orange oil (151 mg, 84%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 0.88 (t, J=7.36 Hz, 3H), 1.27 (m, 2H), 1.48 (m, 2H), 1.92 (m, 2H), 2.44 (t, J=6.62 Hz, 2H), 3.27 (m, 2H), 4.04 (t, J=5.00 Hz, 2H), 5.73 (m, 2H), 6.66 (s, 1H). LC-MS RT: 2.13 min, m/z=, 223.0, Method A.

(2R)-2-[(2-amino-7,8-dihydro-6H-pyrano[3,2-d]pyrimidin-4-yl)amino]hexan-1-ol (14, a compound according to Formula (III)). A mixture of 4-chloro-7,8-dihydro-6H-pyrano[3,2-d]pyrimidin-2-amine (90 mg, 0.485 mmol) and D-norleucinol (227 mg, 1.94 mmol) in 1,4-dioxane (2.4 mL) was heated at 115° C. for 20 h, then the reaction mixture was cooled to rt, then concentrated under reduced pressure. The crude was purified by silica gel column chromatography using a CH₂Cl₂/(CH₃OH containing 5% aq. NH₃) gradient to give the titled compound as a viscous yellow oil (92 mg, 71%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 0.85 (t, J=6.57 Hz, 3H), 1.15-1.335 (m, 4H), 1.42 (m, 1H), 1.57 (m, 1H), 1.92 (m, 2H), 2.42 (t, J=6.13 Hz, 2H), 3.34 (m, 1H), 3.41 (m, 1H), 3.93-4.09 (m, 3H), 4.67 (t, J=4.57 Hz, 1H), 5.42 (s, 2H) 5.77 (d, J=9.09 Hz, 1H). LC-MS RT: 1.99 min, m/z=267.0, Method A. [α]_(D) ²⁰+15 (c 0.26, DMF).

LC-MS Methods.

The LC measurement was performed using a UPLC Acquity (Waters) system comprising a binary pump with degasser, an autosampler, a diode-array detector (DAD) and a column as specified in the method below, the column is held at a temperature of 40° C. Flow from the column was brought to an MS detector. The MS detector was configured with an electrospray ionization source. The capillary needle voltage was 3 kV and the source temperature was maintained at 130° C. on the Quattro (triple quadrupole mass spectrometer from Waters). Nitrogen was used as the nebulizer gas. Data acquisition was performed with a Waters-Micromass MassLynx-Openlynx data system.

Method A. Reversed phase UPLC was carried out on a Waters Acquity BEH (bridged ethylsiloxane/silica hybrid) C18 column (1.7 μm, 2.1×100 mm) with a flow rate of 0.343 mL/min. Two mobile phases (mobile phase A: 95% 7 mM ammonium acetate/5% acetonitrile; mobile phase B: 100% acetonitrile) were employed to run a gradient condition from 84.2% A and 15.8% B (hold for 0.49 minutes) to 10.5% A and 89.5% B in 2.18 minutes, hold for 1.94 min and back to the initial conditions in 0.73 min, hold for 0.73 minutes. An injection volume of 2 μL was used. Cone voltage was 20V for positive and negative ionization mode. Mass spectra were acquired by scanning from 100 to 1000 in 0.2 seconds using an interscan delay of 0.1 seconds.

Biological Activity of Compounds of Formula (I, II, III)

Assessment of human TLR7 and human TLR8 activity. The ability of compounds to activate human TLR7 and/or TLR8 was assessed in a cellular reporter assay using HEK293 cells transiently transfected with a TLR7 or TLR8 expression vector and NFkB-luc reporter construct.

Briefly, HEK293 cells were grown in culture medium (DMEM supplemented with 10% FCS and 2 mM glutamine). For transfection of cells in 15 cm dishes, cells were detached with Trypsin-EDTA, transfected with a mix of CMV-TLR7 or TLR8 plasmid (1700 ng), NFkB-luc plasmid (850 ng) and a transfection reagent and incubated for 48 h at 37° C. in a humidified 5% CO₂ atmosphere. Transfected cells were then washed in PBS, detached with Trypsin-EDTA and resuspended in medium to a density of 1.25×10⁵ cells/mL. Forty microliters of cells were then dispensed into each well in 384-well plates, where 200 nL of compound in 100% DMSO was already present. Following 6 hours incubation at 37° C., 5% CO₂, the luciferase activity was determined by adding 15 μL of Steady Lite Plus substrate (Perkin Elmer) to each well and readout performed on a ViewLux ultraHTS microplate imager (Perkin Elmer). Dose response curves were generated from measurements performed in quadruplicates. Lowest effective concentrations (LEC) values, defined as the concentration that induces an effect which is at least two fold above the standard deviation of the assay, were determined for each compound.

Compound toxicity was determined in parallel using a similar dilution series of compound with 40 μL per well of cells transfected with the CMV-TLR7 construct alone (1.25×10⁵ cells/mL), in 384-well plates. Cell viability was measured after 6 hours incubation at 37° C., 5% CO₂ by adding 15 μL of ATP lite (Perkin Elmer) per well and reading on a ViewLux ultraHTS microplate imager (Perkin Elmer). Data was reported as 0050.

In parallel, a similar dilution series of compound was used (200 nL of compound in 100% DMSO) with 40 μL per well of cells transfected with NFKB-luc reporter construct alone (1.25×10⁵ cells/mL). Six hours after incubation at 37° C., 5% CO₂, the luciferase activity was determined by adding 15 μL of Steady Lite Plus substrate (Perkin Elmer) to each well and readout performed on a ViewLux ultraHTS microplate imager (Perkin Elmer). Counterscreen data is reported as LEC.

TABLE 2 Biological activity of compounds of formula (I, II, III). Compound Human TLR 7 Human TLR 8 # (LEC) μM (LEC) μM 3 14.8 1.0 4 >100 1.3 7 4.7 0.5 8 >100 1.4 13 0.8 0.1 14 32.5 0.1

All compounds showed no activity (LEC>25 μM) in the HEK 293 NF-kB counterscreen assay described above. 

The invention claimed is:
 1. A method of treating viral hepatitis in which the activation of TLR7 and/or TLR8 is involved in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a compound of formula (I), (II) or (III) having the structure

or a pharmaceutically acceptable salt, tautomer, stereo-isomeric form, or solvate thereof, wherein R₁ is C₁₋₆ alkyl substituted by one or more substituents independently selected from hydroxyl or C₁₋₃alkoxy; R₂ is selected from hydrogen, fluorine, C₁₋₃ alkyl, cyclopropyl, —CF₃, C₁₋₃alkoxy or nitrile.
 2. A method of treating viral hepatitis in which the activation of TLR7 and/or TLR8 is involved in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a compound having a structure selected from the group consisting of:

or a pharmaceutically acceptable salt, tautomer, stereo-isomeric form, or solvate thereof.
 3. The method of claim 1, wherein the activation of TLR8 is involved in the subject in need thereof.
 4. The method of claim 1, wherein R₁ is C₁₋₆ alkyl substituted by hydroxyl.
 5. The method of claim 1, wherein R₁ is C₆alkyl substituted by hydroxyl.
 6. The method of claim 1, wherein R₁ is:


7. The method of claim 1, wherein R₁ is:


8. The method of claim 1, wherein R₂ is hydrogen.
 9. The method of claim 2, wherein the activation of TLR8 is involved in the subject in need thereof.
 10. A method of activating human TLR7 and/or TLR8 in a subject, comprising administering to the subject an effective amount of a compound of formula (I), (II) or (III) having the structure

or a pharmaceutically acceptable salt, tautomer, stereo-isomeric form, or solvate thereof, wherein R₁ is C₁₋₆ alkyl substituted by one or more substituents independently selected from hydroxyl or C₁₋₃alkoxy; R₂ is selected from hydrogen, fluorine, C₁₋₃ alkyl, cyclopropyl, —CF₃, C₁₋₃alkoxy or nitrile.
 11. The method of claim 10, wherein the compound has a structure selected from the group consisting of:

or a pharmaceutically acceptable salt, tautomer, stereo-isomeric form, or solvate thereof. 